Linked List generic array creation error undirected graph Java

Question

so I'm trying to look for paths in an undirected graph using java. I feel like I'm maybe on the right track, pretty close to getting it, however, I keep running into a road block and get an error saying. I am using linked lists to store edges and verticies.

Graph2.java:17: error: generic array creation adj = new LinkedList[v];

Here's my code

import java.io.*;
import java.util.*;
import java.util.LinkedList;
import java.util.Scanner;

// This class represents a directed graph using adjacency list
// representation
class Graph2
{
    private int V;   // No. of vertices
    private LinkedList<Integer> adj[]; //Adjacency List

    //Constructor
    Graph2(int v)
    {
        V = v;
        adj = new LinkedList<Integer>[v];
        for (int i=0; i<v; ++i)
            adj[i] = new LinkedList<Integer>();
    }

    //Function to add an edge into the graph
    void addEdge(int v,int w)  {   adj[v].add(w);   }

    //prints BFS traversal from a given source s
    Boolean isReachable(int s, int d)
    {
        LinkedList<Integer>temp;

        // Mark all the vertices as not visited(By default set
        // as false)
        boolean visited[] = new boolean[V];

        // Create a queue for BFS
        LinkedList<Integer> queue = new LinkedList<Integer>();

        // Mark the current node as visited and enqueue it
        visited[s]=true;
        queue.add(s);

        // 'i' will be used to get all adjacent vertices of a vertex
        Iterator<Integer> i;
        while (queue.size()!=0)
        {
            // Dequeue a vertex from queue and print it
            s = queue.poll();

            int n;
            i = adj[s].listIterator();

            // Get all adjacent vertices of the dequeued vertex s
            // If a adjacent has not been visited, then mark it
            // visited and enqueue it
            while (i.hasNext())
            {
                n = i.next();
                System.out.println(n);
                // If this adjacent node is the destination node,
                // then return true
                if (n==d)
                    return true;

                // Else, continue to do BFS
                if (!visited[n])
                {
                    visited[n] = true;
                    queue.add(n);
                }
            }
        }

        // If BFS is complete without visited d
        return false;
    }

    // Driver method
    public static void main(String args[])
    {
        // Create a graph given in the above diagram
        Graph g = new Graph(9999999);
        try{
        File file = new File("Graph.txt");
        Scanner scan = new Scanner(file);
        while(scan.hasNextLine())
        {
            String [] tempArray = scan.nextLine().split(",");
            g.addEdge(Integer.parseInt(tempArray[0]), Integer.parseInt(tempArray[1]));
        }
        scan.close();
    }
    catch(FileNotFoundException fs)
    {

    }

        int u = 1;
        int v = 891950;
        if (g.isReachable(u, v))
            System.out.println("There is a path from " + u +" to " + v);
        else
            System.out.println("There is no path from " + u +" to " + v);;
    }
}

Answer 1

The correct way of declaring this variable is:

private LinkedList<Integer> adj;

Initializing:

adj = new LinkedList<Integer>();

To put an element to this list you can use:

adj.add(index, element);

Element might be LinkedList object, but you should change generic type to LinkedList while declaring.
Read more about LinkedList in Java docs.